[Freeswitch-dev] Normalizing sound files

Wasim Baig wasim at convergence.pk
Wed May 28 23:17:28 EDT 2008

We used to do the following for prompts

   1. noise gate, say at -40db with a fairly quick attack
   2. normalize, or use a compressor with agc
   3. trim both ends silence
   4. add .25 seconds of silence on both ends (may want to skip this for
   5. depending on the media, you can use eq to get rid of say everything
   below 300hz for gsm, etc, its a good idea to boost the highs and cut the
   lows at this time also for crySStal clear prompts (opposite of a de-esser)

this can all be automated through sox or soundforge

On 5/28/08, Michael Collins <mcollins at fcnetwork.com> wrote:
> You rock da hizzouse!
> ________________________________
> From: freeswitch-dev-bounces at lists.freeswitch.org
> [mailto:freeswitch-dev-bounces at lists.freeswitch.org] On Behalf Of Brian
> West
> Sent: Wednesday, May 28, 2008 2:51 AM
> To: freeswitch-dev at lists.freeswitch.org
> Subject: Re: [Freeswitch-dev] Normalizing sound files
> http://svn.freeswitch.org/svn/sounds/trunk/en/us/callie/dist.sh
> That script with sox shows how we do this.
> On May 28, 2008, at 2:36 AM, Michael Collins wrote:
> When you get new prompts you mentioned that you "normalize" them so that
> the sound level doesn't vary from one prompt to the next.  I have a set
> of prompts that GM Voices recorded specifically for me, but I haven't
> normalized them yet.  Could you let me know what process you use for
> this?

wasim h. baig | principal consultant | convergence pk | +92 300 8508070
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